High-latitude Observations of Dissipation-range Turbulence by the Ulysses Spacecraft during the Solar Minimum of 1993–96: The Spectral Break and Anisotropy
Year: 2024
Type: article
Abstract: We examine Ulysses magnetic field observations from 1993 to 1996 as the spacecraft made its first fast-latitude scan from the southern to the northern hemisphere. Most of the observations we use are representative of high-latitude solar minimum conditions. We examine magnetic field power spectra characteristics of interplanetary turbulence at high frequencies, where the spectrum breaks from an inertial range into the ion dissipation range. The onset and spectral index of the dissipation spectrum are consistent with low-latitude observations at 1 au. Both ranges have a ratio of power in perpendicular magnetic field components to parallel components near 3. The power spectrum ratio test developed by Bieber et al. for single-spacecraft analyses that determines the underlying anisotropy of the wave vectors yields only marginally more energy associated with field-aligned wave vectors than perpendicular wave vectors when comparing the inertial and dissipation-range spectra. The lack of significant change in the anisotropies between the inertial and dissipation ranges contrasts strongly with the turbulence found typically for 1 au near-ecliptic observations, where significant differences in both anisotropies are observed.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: Quasilinear Dissipation of Turbulently-Generated Kinetic Alfven Waves: Kinetics of Ion Heating and Solar Wind Acceleration in Coronal Holes, EXTENSIVE RESEARCH SHOWS THAT PARTICLES IN A WIDE RANGE OF PLASMA ENVIRONMENTS THROUGHOUT THE HELIOSPHERE SOLAR CORONA AND MAGNETOSPHERE DEVIATE FROM TRADITIONALLY ASSUMED GAUSSIAN DISTRIBUTIONS. OBSERVED DISTRIBUTIONS SHOW LARGE SUPRATHERMAL COMPONENTS THAT MAY EXERT NON-NEGLIGIBLE INTERNAL PRESSURE WITHIN THE PLASMA. UNDERSTANDING THE RELATIONSHIPS BETWEEN SUPRATHERMAL ION POPULATIONS AND COMMONLY OCCURRING PHENOMENA SUCH AS WAVE-PARTICLE INTERACTIONS TURBULENCE MAGNETIC RECONNECTION SHOCK WAVES AND PLASMA COMPRESSIONS REMAINS A MISSING YET ESSENTIAL ELEMENT OF PLASMA DYNAMICS THAT APPLIES THROUGHOUT THE HELIOSPHERE MAGNETOSPHERE AND OTHER PLANETARY ENVIRONMENTS. UNDERSTANDING SUPRATHERMAL DISTRIBUTIONS IS REQUIRED TO MAKE SENSE OF: IBEX AND VOYAGER OBSERVATIONS IN THE HELIOSHEATH; OBSERVATIONS OF SUPRATHERMAL PARTICLES IN FAST AND SLOW SOLAR WIND AND UPSTREAM OF EARTH S BOW SHOCK. ESTABLISHING THE THEORETICAL UNDERPINNINGS OF SUPRATHERMAL DISTRIBUTIONS WILL BE NECESSARY FOR FUTURE OBSERVATIONS FROM SOLAR ORBITER (SO) SOLAR PROBE PLUS (SPP) AND THE INTERSTELLAR MAPPING AND ACCELERATION PROBE (IMAP). HERE OUR OBJECTIVE IS TO DETERMINE THE ORIGIN OF SUPRATHERMAL ION DISTRIBUTIONS AND THE PHYSICAL PROCESSES THAT CREATE THEM. THIS WORK ANSWERS FUNDAMENTAL SCIENCE QUESTIONS IN BASIC PLASMA PHYSICS AND PROVIDES THE MISSING LINK BETWEEN BULK PLASMA IN THERMAL EQUILIBRIUM AND NON-EQUILIBRIUM PROCESSES SUCH AS DIFFUSIVE SHOCK ACCELERATION WHICH CREATES HIGH-ENERGY PARTICLES. OUR WORK INVESTIGATES A COMPELLING PROBLEM ADDRESSING THE FOURTH OF THE HIGH-LEVEL SCIENCE GOALS FROM THE HELIOPHYSICS DECADAL SURVEY: [TO] DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE. OUR LACK OF A DETAILED UNDERSTANDING OF THE ORIGIN OF SUPRATHERMAL ION POPULATIONS THWARTS PROGRESS IN HELIOPHYSICS. A BASIC FRAMEWORK FOR DESCRIBING SUPRATHERMAL ION DISTRIBUTIONS IS NEEDED TO SOLVE SIGNIFICANT PROBLEMS RANGING FROM THE ORIGIN OF THE IBEX RIBBON TO THE INJECTION OF SEED PARTICLES AT CORONAL AND INTERPLANETARY SHOCKS TO FORM SOLAR ENERGETIC PARTICLES. THEREFORE A DEDICATED INVESTIGATION IS REQUIRED TO ESTABLISH THE ORIGIN OF SUPRATHERMAL ION POPULATIONS ENCOMPASSING DIVERSE HELIOSPHERIC PLASMA REGIMES AND DOMAINS. WE ANSWER FOUR SCIENCE QUESTIONS: HOW DO TURBULENCE WAVES AND STOCHASTIC PROCESSES CREATE NON-MAXWELLIAN ION DISTRIBUTIONS? HOW DO SHOCKS COMPRESSION REGIONS AND MAGNETIC RECONNECTION PARTICIPATE IN ENERGIZING SUPRATHERMAL IONS AND HOW MIGHT THESE PARTICLES FILL THE HELIOSPHERE? WHAT ARE THE BASIC ANALYTICAL FRAMEWORKS IN WHICH NON-EQUILIBRIUM PROCESSES CAN BE DESCRIBED? AND WHAT OBSERVATIONAL CHARACTERISTICS CAN BE USED TO DISTINGUISH BETWEEN LOCAL NON-EQUILIBRIUM ION ACCELERATION PROCESSES AND NON-LOCAL TRANSPORT EFFECTS? WE PROPOSE A UNIFIED APPROACH IN WHICH WE TEST THEORIES THROUGH NUMERICAL SIMULATIONS COMPARE THE RESULTS WITH OBSERVATIONS IN DIFFERENT PARTS OF THE HELIOSPHERE AND MAKE PREDICTIONS FOR MEASUREMENTS BY FUTURE NASA MISSIONS. WE RELY ON HYBRID (ION SCALE) SIMULATIONS COMPLEMENTED BY SELECTED FULL KINETIC (ELECTRON SCALE) SIMULATIONS TO TEST HOW DIFFERENT PROCESSES CAN ACCELERATE SUPRATHERMAL POPULATIONS ON DIFFERENT SCALES. IN PARALLEL WE DEVELOP ANALYTICAL FRAMEWORKS TO UNDERSTAND HOW REALISTIC SUPRATHERMAL ACCELERATION MECHANISMS MODIFY THE SUBSEQUENT ACCELERATION TO 100S OF KEV OR ABOVE. THIS ALLOWS US TO DEVELOP A KINETIC TRANSPORT MODEL THAT IS COUPLED TO GLOBAL MHD SIMULATIONS. WE COMPARE RESULTS FROM THESE GLOBAL SIMULATIONS WITH OBSERVATIONS FROM NASA HELIOPHYSICS SYSTEM OBSERVATORY (HSO) AND MAKE PREDICTIONS FOR SPP SO AND IMAP., FESD Type 1: Sun to Ice--Impacts on Earth of Extreme Solar Events, INTERSTELLAR NEUTRAL ATOMS IN THE 3D HELIOSPHERE: DETAILED MODELING., PLASMA TURBULENCE IS A FUNDAMENTAL PROCESS IN THE SOLAR WIND WHICH INFLUENCES AND REGULATES THE BEHAVIOR AND EVOLUTION OF THIS MEDIUM. TURBULENCE IN THE INNER HELIOSPHERE APPEARS TO BE A COMBINATION OF DECAYING TURBULENCE FROM THE SUN AND DRIVEN TURBULENCE FROM SHEARS OR TEMPORAL DISTURBANCES. FURTHER OUT IT IS CLEAR THAT FLUCTUATION ENERGY CONTINUES TO BE ADDED TO THE TURBULENT CASCADE BUT BEYOND ~ 10 AU THE DRIVING IS DUE TO INSTABILITIES WHICH ACT TO ISOTROPIZE NEWLY-IONIZED INTERSTELLAR PICKUP IONS (PUI). THIS ENERGY SOURCE IS DISTINCT FROM THE LARGE-SCALE STIRRING THAT IS ASSUMED IN HYDRODYNAMIC AND MHD TURBULENCE THEORIES. PUI INSTABILITIES GENERATE FLUCTUATIONS WITH HIGH WAVENUMBERS IN THE INERTIAL RANGE AND WAVEVECTORS DIRECTED PRIMARILY ALONG THE LARGE-SCALE MAGNETIC FIELD. THESE PUI-GENERATED WAVES HAVE BEEN OBSERVED AND WE HAVE SHOWN THAT THEY ARE USUALLY SUBSUMED INTO THE TURBULENT CASCADE. THIS TURBULENCE CONTINUES TO HEAT THE SOLAR WIND OUT TO THE TERMINATION SHOCK BUT THERE IS EVIDENCE THAT THE TURBULENT BEHAVIOR IS SIGNIFICANTLY DIFFERENT FROM THAT NEAR 1 AU. THUS THE TURBULENT PROCESSES IN MOST OF THE HELIOSPHERE ARE DRIVEN BY PUIS BUT THE MODIFICATIONS DUE TO THIS INERTIAL-RANGE DRIVING HAVE NOT BEEN STUDIED. WE PROPOSE AN EXTENSIVE PROGRAM OF INVESTIGATIONS INVOLVING HYBRID SIMULATIONS DATA ANALYSIS AND THEORETICAL MODELING TO EXPLORE THIS PUI DRIVING. SPECIFICALLY: - WE WILL ADAPT OUR EXISTING 3D HYBRID SIMULATION OF PLASMA TURBULENCE BY ADDING AN ION-CYCLOTRON-WAVE ENERGY SOURCE WITHIN THE TURBULENT INERTIAL RANGE. WE WILL START WITH A FULLY-DEVELOPED TURBULENT SYSTEM AND INVESTIGATE THE EFFECTS OF DRIVING AT PARALLEL WAVENUMBERS APPROPRIATE TO THIS PUI DRIVING. - WE WILL ANALYZE THE COMBINED PARTICLE AND FIELD DATA FROM VOYAGER 2 CONSTRUCTING FLUCTUATION SPECTRA OF MAGNETIC FIELD PLASMA VELOCITY AND DENSITY GENERATING NEW DATA PRODUCTS IN THE OUTER SOLAR WIND. WE WILL EXAMINE THE PROPERTIES OF THE THIRD-ORDER STRUCTURE FUNCTION WHICH PROVIDES INFORMATION ON THE ENERGY TRANSPORT BY THE TURBULENT CASCADE. THROUGH THIS STRUCTURE FUNCTION ANALYSIS WE WILL ALSO OBTAIN EMPIRICAL TURBULENT DISSIPATION RATES THAT WE WILL COMPARE WITH THE OBSERVED PROTON TEMPERATURES TO TEST THE VALIDITY OF TURBULENT HEATING IN THIS REGION. WE WILL IDENTIFY SIMILARITIES AND DIFFERENCES BETWEEN THE TURBULENCE DRIVEN AT LARGE SCALE AS SEEN IN THE INNER HELIOSPHERE AND THE INERTIAL-RANGE DRIVING TAKING PLACE BEYOND 10 AU. - WE WILL EXPAND OUR MODEL OF SOLAR WIND HEATING BY PICKUP PROTONS TO INCLUDE THE EFFECTS OF NEWLY-IONIZED INTERSTELLAR PICKUP HE + WHICH IS SEEN TO PRODUCE ITS OWN WAVES AND TO MODIFY THE SCATTERING OF THE INTERSTELLAR PICKUP PROTONS. IN PARTICULAR WE WILL DETERMINE WHETHER THE DISTINCT RESONANT PROPERTIES AND WAVE-PARTICLE INTERACTIONS OF PICKUP HELIUM AND OTHER HEAVY IONS COULD RESULT IN PREFERENTIAL FERMI ACCELERATION OF THESE IONS POTENTIALLY EXPLAINING THE OVER-ABUNDANCE OF HEAVY IONS IN ANOMALOUS COSMIC RAYS. THE PROPOSED RESEARCH WILL ADVANCE THE NASA STRATEGIC GOALS TO "EXPLORE THE PHYSICAL PROCESSES IN THE SPACE ENVIRONMENT ... THROUGHOUT THE SOLAR SYSTEM" AND TO "ADVANCE OUR UNDERSTANDING OF THE CONNECTIONS THAT LINK THE SUN ... AND THE OUTER REACHES OF OUR SOLAR SYSTEM". IT WILL ALSO ADDRESS THE HELIOPHYSICS DECADAL SURVEY GOALS TO "DETERMINE THE INTERACTION OF THE SUN WITH THE SOLAR SYSTEM AND THE INTERSTELLAR MEDIUM" AND TO "DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE"., G5642819733, VOYAGER MAG OBSERVATIONS AT KINETIC SCALES: PICKUP ION WAVES AND TURBULENCE FROM 1 TO 35 AU SCIENCE GOALS AND OBJECTIVES: WE PROPOSE TO EXAMINE THE, G951740287
OpenAlex ID: W4403192453